STRETCH FABRICS MAKE FASHION COMFORTABLE

By BERNADINE MORRIS

Published: May 5, 1987

They do not assault your senses like very short skirts, the most visible trend of the new season. In fact you hardly know they are there. But stretch fabrics are probably the most important new development in fashion, and they have the potential to change radically the way people look and feel in the clothes they wear.

''It's the new technology being translated to modern living,'' said Calvin Klein. ''It is going to revolutionize fashion. All the mills all over the world are adding stretch fibers to their wool or silk yarns.''

''We can fit clothes more snugly so women can move as freely as if they had nothing on,'' said Donna Karan. ''It's an extension of wool jersey, which is my favorite fabric because it has a built-in elasticity. But the difference is the new stretch materials do not pull out of shape. Jersey pants can eventually bag at the knees. Stretch fabrics do not.''

These two are among the many designers in this country and abroad who have used significant amounts of stretch fabrics in their fall and winter collections. For Mr. Klein, it made possible the long, lean body line that is the key to his current silhouette. He used stretch fabrics for skinny pants and snug tops for day and velvet skirts and pants for evening. The over-the-knee boots and tights he showed also stretched.

Not every woman who tries on the new clothes will be aware of the stretch content. ''They may just think they are more comfortable,'' Mr. Klein said.

''It may not be for everyone yet,'' he conceded. ''It's for the woman who is looking for the newest, most modern way to dress. The people who are exercising and watching their diet are going to relate to this.''

Ms. Karan said she believes there is another important advantage.

''Stretch clothes provide control to the body, smoothing out bumps the way girdles used to do,'' she said. Women are familiar with the feeling through control-top tights, she added.

Spandex, the synthetic fiber that provides elasticity when added to natural materials like silk and wool, was first used in girdles and bras. It was also popular in ski pants in the 1940's.

David Cameron discovered some old ski fabric made by Bianchini, a French fabric company, and liked the way it could be tailored. He persuaded the company to revive the material and used it for an important part of his fall collection. It appears in short jackets decorated with zippers as well as in coats, A-line and straight skirts and pants.

He was attracted to the material because it had a hard-edged ''futuristic'' look, Mr. Cameron said; the stretch properties were incidental. Because the material is water-repellent, it is possible to ski in the clothes.

Geoffrey Beene's use of stretch materials was esthetic as well as practical. Instead of the usual taffeta lining for a purple and black tweed jump suit, he used stretch jersey. It made it possible to cut the jump suit closer to the body, giving it a sleek fit.

He also created his own fabric, which resembles Persian lamb, by stitching satin on a stretch base. He used it for lightweight jackets with the three-dimensional look of fur.

Still another use was stretch inserts at the midriff and back of dresses in silk and wool satin, to draw the dress closer to the body and activate a curvier look.

''Not every stretch fabric we tried worked properly,'' Mr. Beene said. ''Some were too scratchy, some too heavy. But stretch certainly will be a component of fashion's immediate future.''

Ms. Karan pointed out that some fabrics stretched too much and some not enough.

''The problem is getting just the right amount of give,'' she said. ''This of course varies with the style.'' Wool crepe, cavalry twill and a cashmere and wool velour were her favorites for fall. She is now working with cotton for the resort season. New Techniques Required

New dressmaking techniques have to be developed to handle the new stretch materials. Patterns must be cut differently to allow for the stretch. Some clothes that appeared on the runways made the models look like stuffed sausages; others bunched up unattractively when the models walked.

But ultimately it may be possible to cut fewer sizes to fit more women, designers predict. Meanwhile, retailers approve the handling of stretch materials in the new collections.

''We started last season with some stretch styles from Gaultier in Paris and they were a hit with the very young,'' said Thomas A. Marotta, vice president of Nan Duskin, checking out the new fashions. ''Now it looks more controlled, and the effect is far more subtle. The clothes do not scream 'stretch.' I think when the customers try on the clothes and see how they mold the body, they will be impressed.''